This invention relates to a thermomagnetic recording device for recording information such as sounds and pictures on a magnetic layer having magnetic anisotropy in a direction perpendicular to the surface thereof and temperature-dependent coercive force.
Thermomagnetic recording devices of this type can perform high-density recording with markedly higher efficiency, as compared with devices having a ring-shaped magnetic head which is conventionally used in combination with a magnetic disk or the like. In such a recording operation, a magnetic layer is heated by spot-irradiation with a laser beam, the coercive force of a heated portion is reduced by utilizing the temperature-dependence of the coercive force of the magnetic layer, and a signal field is applied to such portion for magnetic recording.
In order to increase the recording density with these recording devices, it is necessary to reduce the enlargement of a magnetized region by delicate control of the laser beam and control of the applied magnetic field. Presently, however, it is hard to apply the laser beam to a limited region. Moreover, it is quite difficult to magnetize a very limited region with few magnetic field components along a direction perpendicular to the magnetic layer, because the magnetic layer is liable to be heated so that the temperature may be gradually lowered from the beam center of the laser beam toward the periphery thereof, thereby extending the magnetizable region, and because a signal field is applied by means of a notched ring-shaped magnetic head. Thus, the magnetized region becomes relatively large, so that the playback resolution and recording efficiency will be deteriorated.